This project is studying the enzyme 3-hydroxy-3-methylglutaryl coenzyme. A reductase (HMG-CoA reductase), the main regulatory enzyme in cholesterol biosynthesis. An affinity chromatography procedure has been developed for the purification of this enzyme from rat liver microsomes. The stability or lability of this enzyme is also under investigation. BIBLIOGRAPHIC REFERENCES: Tormanen, C.D., Ackerman, M.E., Redd, W.L. and Scallen, T.J. "Activation of 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) Reductase by NADPH" Federation Proc. 34, 560 (1975). Tormanen, C.D., Redd, W.L., Srikantaiah, M.V. and Scallen, T.J. "Purification of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase". Biochem. Biophys. Res. Commun.. 1976, in press.